| Products > Test Equipment |
| Oscilloscope input noise comparison |
| << < (12/27) > >> |
| _Wim_:
Ok, done quick a few tests. Setup: CMU200 signal generator connected to Pico 5442B with 50 ohm input adaptor. First: 8 bit mode (1GS/s), my scope has 60Mhz bandwidth * reference signal at 5Mhz (500mV RMS) * -3db found at 87Mhz * -6db at 200Mhz * -10db at 300Mhz * -10db also at 400Mhz * when switching to 200mV/div sensitivity, signal drops completely (this path has much lower bandwidth) Second: 16-bit mode (62.5MS/s) * reference signal at 5Mhz (500mV RMS) * at 57.5 Mhz we see a 5 Mhz alias only 3db down (no bandwidth limit) * at 57.5 Mhz with 20Mhz bandwidth limit we see a 5Mhz alias 10db down => 20Mhz bandwidth limit only 6db/oct or less filter slope? So indeed much higher bandwidth noise can come back into the spectrum under test, and the software should at least active the 20Mhz bandwidth limit automatically when running at 62.5MS/s only. |
| MrW0lf:
--- Quote from: _Wim_ on November 02, 2018, 08:53:02 am ---So indeed much higher bandwidth noise can come back into the spectrum under test, and the software should at least active the 20Mhz bandwidth limit automatically when running at 62.5MS/s only. --- End quote --- And what if you want to actually use alias? The problem cannot be handled properly with 20MHz limit anyway so better leave it alone. AFAIK they disabled FFT plot > official analog bw not to confuse dumbusers. So now you cannot look 101MHz peak on -3dB@~140MHz scope etc :palm: |
| _Wim_:
--- Quote from: MrW0lf on November 02, 2018, 09:26:56 am ---So now you cannot look 101MHz peak on -3dB@~140MHz scope etc :palm: --- End quote --- Why not, you know were it will fold back to, so you still can but just need to calculate a bit... |
| MrW0lf:
--- Quote from: _Wim_ on November 02, 2018, 09:31:53 am ---Why not, you know were it will fold back to, so you still can but just need to calculate a bit... --- End quote --- ...with scope running at 1GSa/s? I would sort of get it if they handicapped dedicated FFT only which has auto control over sampling rate, but no. It's also imposed on FFT viewport. Also FFT is completely disabled for ETS :rant: So sorry but these boxes already have enough of dumb (or perhaps marketing derived?) limitations. |
| _Wim_:
--- Quote from: MrW0lf on November 02, 2018, 09:40:08 am ---...with scope running at 1GSa/s? I would sort of get it if they handicapped dedicated FFT only which has auto control over sampling rate, but no. It's also imposed on FFT viewport. Also FFT is completely disabled for ETS :rant: So sorry but these boxes already have enough of dumb (or perhaps marketing derived?) limitations. --- End quote --- Ok, but now you are suggesting they deliver you a 500Mhz product for the price of a 60Mhz product, I am off course also a fan of that (but would be bad marketing). I think almost all base scopes are just a software cripled version of the high bandwidth model of the same series, this is not only so for pico, but is the case for all brands. |
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